Project Summary Mutations in the LMNA gene, which encodes type-A lamin proteins that constitute the nuclear lamina network, cause a broad spectrum of diseases collectively called laminopathies. LMNA is one of the most frequent genes involved in dilated cardiomyopathy (DCM), an incurable disease characterized arrhythmias and sudden cardiac death. How mutations in LMNA cause DCM is poorly understood. In the mammalian genome, lamin A interacts with chromatin in a cell-specific manner at lamina-associated domains (LADs) at the nuclear periphery, suggesting a key role for lamin A proteins in the overall genome integrity and transcriptional regulation. However, where and how lamin A interacts with the genome and whether DCM-causing lamin A mutations rearrange the genome architecture in DCM remains elusive. The central hypothesis of this proposal is that a subset of LMNA mutations cause DCM through loss of structural function of lamin A, leading to spatial reorganization of the genome architecture and aberrant gene expression. This hypothesis is based on strong preliminary data showing that a DCM LMNA mutation causes haploinsufficiency and triggers genome-wide changes in LADs concomitantly with aberrant gene expression in patient-specific human induced pluripotent stem cells derived cardiomyocytes (iPSC-CMs). Together our data suggest a mechanistic link between the dysregulation of genome integrity and the DCM phenotype. The overarching goal of the study is to understand the molecular etiology responsible for the cardiac-specific phenotypes caused by LMNA mutations and to demonstrate that impaired lamin A chromatin- and protein-interactions cause DCM. In Aim 1 we will validate the disruption of the 3D genome reorganization as a causative mechanism of LMNA-related DCM. In Aim 2 we will decipher the molecular basis of calcium dysregulation and arrhythmia in LMNA DCM, and in Aim 3 we will develop a therapeutic strategy by modulating the local genome organization. We provided compelling preliminary data to support the soundness of our hypothesis-driven research proposal. We have assembled a multidisciplinary team and we are well positioned to achieve the project goals within four years. If successful, our studies will provide a new paradigm for understanding the pathogenesis and pave the way for targeted therapies for LMNA-related DCM.